Edge card connectors are used for connecting a circuit board with conductive pads along a lower edge, such as a daughter circuit board or a daughter card, to an underlying circuit board, such as a mother circuit board. Terminals loaded in a housing of the connector along a slot for receiving the daughter circuit board connect the conductive pads on the daughter circuit board to conductors on the mother board. Edge card connectors typically employ a lever disposed at one side of a housing of the connector, which is rotated inwardly to latch the daughter circuit board in a slot in the connector and rotated outwardly to eject the daughter circuit board from the slot in the connector.
The levers for such card edge connectors sometimes undesirably rotate or swivel in a plane which is perpendicular to a plane defined by the intended rotational movement of the lever. The plane of rotational movement is normally parallel to the slot in the connector. The undesirable rotation or swiveling of the lever is aggravated when the lever is subjected to lateral forces which are typical in the manufacturing, assembly and shipping of these connectors. Such lateral forces can cause the lever to excessively rotate or swivel thereby unfortunately causing damage to the lever.
These levers are also prone to vibration. As a result of vibration, the contact impedance between the conductive pads of the daughter circuit board and the terminals in the connector can become unstable.
FIG. 8 shows a conventional edge card connector according to U.S. Pat. No. 5,470,240. The structure of the edge card connector includes an insulative housing 1, a plurality of conductive contacts 3 mounted in the insulative housing 1 for connection to connecting pads of the circuit board (not shown), and two levers 5 pivotally mounted at pivot points 8 on the insulative housing 1 at two opposite ends, respectively. The levers 5 each comprise a wrench arm 7 at the bottom, and a side projection 9 near the top thereof. When the levers 5 are rotated inwardly, the side projections 9 of the levers 5 are engaged into respective side recesses 4 at two opposite side edges of the daughter circuit board 2. To remove the daughter circuit board 2 from the insulative housing 1, one lever 5 is rotated outwardly to disengage the side projection 9 from the corresponding side recess 4, and at the same time the respective wrench arm 7 is rotated upwardly to lift the daughter circuit board 2 from the insulative housing 1. The main drawback of this structure is that the edge card connector has no means to protect the levers against destruction from lateral impact.
FIG. 9 shows another structure of a prior art edge card connector comprising a housing 1' for receiving a daughter circuit board (not shown) to connect contact pads on the circuit board to terminals 3'. A lever 5' has a wrench arm 7' for ejecting the daughter circuit board from the connector 1'. However, this structure is still not satisfactory in function. The expanded opposite end of the insulative housing 1' which is designed to reinforce the structural strength of the insulative housing greatly increases the transverse dimension of the edge card connector. Further, the lever 5' has flanges 9' that are moved by rotation of the levers 5' in and out of the space between respective parallel upright supports 6 of the insulative housing 1' to stabilize movement of the levers 5'. However, when the levers are turned outwardly, the flanges are disengaged from the upright supports, thereby becoming vulnerable to damage from lateral impact.